My daughter ordered a new Ford Fiesta in July, she has just had a call from the dealers saying she needs to pay in full for the car before the end of sept and car will be ready for collection mid October.

They said this is due to car increasing in price next month. Surely not our problem.

I have spoken to dealer and said we will not be paying for the car until we collect it. He said he needs to talk to manager.

Just wanted to know legally where we stand before I kick off with them tomorrow

The price is agreed when you put down the deposit. The monies due and terms of payment will be detailed in your Agreement documents. I have never paid for a car until it is ready. Then cleared funds have to be paid over before collection.
Sounds more like a dealer wanting to hit his 3rd quarter bonus on sales of cars. If so, it is not professional at all. Just adding pressure and stress

And of course the risk you run is that if the dealer goes belly up in the meantime you could have a big job getting your hands on the car from the administrators. Just look at the House of Fraser mess at the moment.

It's a charlatan's trick to try this on with you and your daughter, if this is a Ford main dealership then they should be ashamed of such tactics.

You do not have to pay any final balance until the car is ready to be handed over to you. As Hcblue says, imagine if you did pay everything up-front and then the dealer went bust before they delivered your car, you'd never see your money again!

I was also very surprised to read that it takes about as long to order a new Fiesta as it does to order a Jaguar . . from July to mid October?

. . been enjoying since July '16, 2.0d R-Sport, Ammonite + Black Pack, Jet/Red interior and a few useful options

Not the way you would expect a main dealer too behave and there is no way I would pay till collection day as said if any thing happened to the dealer ship your poor daughter would be in a nightmare situation.
Recently the main dealer my wife buys her cars from (abarth) went under and the money she paid for her service plan was lost as it turned out the plan was ran by the dealer and not the abarth network although this was only a few hundred pounds still been such a hassle trying to recover money from administrators but if it was thousands it would be a nightmare especially for a younger person.

Thanks for all the advice guys, finally sorted. I have told them I will not be paying until collection and if they are not happy I will cancel order. Guess what, that seems to be okay now. Certainly wouldn’t use them again.